This invention is directed to weft yarn control techniques for shuttleless looms, and more specifically to a method and apparatus for controlling the trailing portion of the weft yarn which, as used herein, is the portion of the weft yarn extending from the fabric fell back to the yarn source at the end of each pick of the yarn carrier. This control includes the severing of the trailing weft yarn portion from the inserted portion and the maintaining of the trailing severed portion in proper position for pickup by the yarn insertion element on the successive pick. The severing and clamping steps are accomplished by a stationary apparatus placed in the path of the trailing weft yarn portion during the beat-up operation.
In the operation of a shuttleless loom, a weft yarn is picked up and carried by a carrier or rapier through the shed formed by the warp yarns. The delivery rapier deposits the leading end of the weft yarn in a similar receiving carrier and returns to its home position. Once the weft yarn is inserted in the shed between the upper and lower warp yarns, the loom reed moves forwardly and beats the inserted weft yarn into the fabric fell. During this "beat-up" operation the trailing portion of the weft yarn (hereinafter sometimes referred to as the "non-inserted weft yarn portion") follows the movement of the loom reed from back to front alongside the edge or selvage of the fabric being formed. At some time between successive movements or "picks" of the rapier, it is necessary both to sever the trailing weft yarn portion from the inserted portion and to position the severed end of the non-inserted portion in proper orientation or alignment for engagement by the rapier during its next pick.
The non-inserted weft yarn portion must be controlled at all times and cannot be severed and merely allowed to dangle. Otherwise, the rapier will not pick up the weft yarn on its next pick. If the severing operation occurs too early in the beat-up operation, the inserted weft yarn may loose the tension thereon prior to the time it is gripped between the upper and lower yarns of the yarn shed resulting in unacceptable fabric. On the other hand, if the weft yarn is not severed until after the beat-up operation is completed, the speed of operation may be adversely affected. Secondly, once the weft yarn is severed, the trailing end must be controlled by some type of clamping or gripping device (often called a "transfer" device) and brought into proper alignment in the path of the rapier, so that it is properly seated during the initial stages of the next pick of the rapier (yarn insertion element).
There have been various attempts known to the inventor of the present invention to control the weft yarn, however, generally they involve some type of complicated mechanism which must be moved quickly from one position to another during or subsequent to the beat-up operation. This results in a more complicated and expensive control or transfer mechanism than is desired. Further, the increased number of movable parts leads to potential reliability problems during successive use. Examples of such movable weft yarn control devices are described in the U.S. Pat. Nos. to Budzyna No. 3,899,008 and to Lucian et al 4,338,971.
In the present invention, the control of the trailing weft yarn portion and the severing thereof are effected by substantially stationary devices in response to the forward movement of the weft yarn by the loom reed during the beat-up operation. At the time of completion of the beat-up operation, the trailing weft yarn portion is already severed and held in proper position for being engaged by the carrier on the next pick. There is no need for a repositioning operation which is costly from the standpoint of lost time and more complex mechanisms. At pick speeds of 350-450 picks per minute, it is important to eliminate any time consuming operations which would tend to increase the operating cycle time.
In the apparatus to be herein described, the entire weft yarn control sequence takes place during the beat-up operation. As the loom reed moves forwardly to beat the inserted weft yarn portion into the fabric fell, the non-inserted or trailing portion also moves forwardly alongside the selvage. A first clamping device having a guide surface that lifts the non-inserted weft yarn into a position between a pair of clamping jaws is provided in the path of the trailing weft yarn portion. A flag/proximity switch type timing mechanism then activates a solenoid at the precise moment to cause the clamping jaws to close on the yarn thereunder. Once clamping has been effected and as the movement of the reed continues, the section of the weft yarn portion between the clamping jaws and the selvage continues to move forwardly. A severing device positioned in the path of the aforesaid section engages the weft yarn as it moves forwardly and severs it either by a hot wire or by some type of blade activated by the loom reed.
The weft yarn is thus severed and at this time the severed trailing portion is already under the control of the clamping mechanism. The clamping mechanism and guide surface leading thereinto have been so designed as to position and maintain the severed trailing weft yarn in proper position so that as the yarn insertion element begins its next pick, it engages and seats the leading end of the weft yarn so positioned. This portion of the weft yarn then becomes the leading end for the next pick. At the precise time when the leading end is seated the timing mechanism releases the solenoid and thereby opens the clamping jaws to release the severed end of the weft yarn.
More particularly, the mechanism of the present invention is directed to a unique yarn control apparatus for use in conjunction with shuttleless looms of the type in which a weft yarn is repeatedly inserted into the shed formed by warp yarns at high speeds (350-450 picks per minute). The mechanism is operated responsive to the movement of the loom reed from a first position extending along the path that the inserted weft yarn is initially inserted into the shed forwardly into a second position defined by the fabric fell. The aforementioned clamping device and severing device are stationarily placed in the path of the trailing end of the weft yarn which follows the reed forwardly. As the loom reed moves forwardly, the trailing end of the weft yarn is caused to move up over a guide surface into a stationarily positioned pair of clamping jaws. A timing mechanism activates a solenoid to close the clamping jaws at the prescribed point in time when the weft yarn arrives therebetween. Subsequently, the trailing end of the weft yarn between the clamping device and the edge of the fabric fell is moved further forward into operative engagement with a severing device. The severing device may be either a hot wire (in the case of an all synthetic fabric) or a blade or scissors-type severing device (in the case of natural or blended fibers).
The difference in the control technique of the present invention and known approaches is that here the trailing end of the weft yarn is moved into engagement with a stationary clamping and severing device by the action of the loom reed. Subsequent to the completion of the beat-up operation, there is no mechanism for moving the weft yarn to another position, as the clamped weft yarn trailing end is already properly aligned with and in the path of the weft yarn insertion device, so that it is automatically seated in the carrier on its next pick. At a second prescribed point in time when the weft yarn is seated in the carrier or insertion device, the clamping jaws open responsive to the aforesaid timing mechanism.
It is therefore an object of the present invention to provide an improved weft yarn control mechanism.
It is another object of the present invention to provide an improved weft yarn control mechanism of the type described in which the trailing end of the weft yarn is moved into engagement with a stationary clamp and yarn severing device responsive to the forward movement of the loom reed, and no further positioning or repositioning of the weft yarn is necessary preparatory for the next picking operation.